The present invention relates to a new and improved method for producing a rotating or revolving air layer and, furthermore, pertains to a new and improved false-twist air jet nozzle including at least one twist nozzle for the practice of the method and for producing a false or fluid twisted yarn.
At this point it is observed that in the context of this disclosure, the term "twisted fiber structure" or equivalent expressions, are used in their broader sense to encompass not only a mass of fibers or fiber material to which twist has been applied but also yarn-like structures containing twist and from which there is ultimately produced a yarn.
Generally speaking, the method of the present invention for producing a rotating or revolving air layer is of the type which contemplates producing such rotating air layer in a twist-producing part or component of a twist nozzle of a false-twist air jet nozzle and using such rotating air layer for placing a twisted fiber structure or yarn-like structure into rotational or rotary movement.
As to the false-twist air jet nozzle of the present invention, sometimes also simply briefly referred to as an air jet nozzle, such is of the type containing at least one twist nozzle generally comprising a central inlet duct or channel through which there is infed the twisted fiber structure or the like and which is followed by a twist-producing part or component of generally round cross-section. There is further provided at least one air injection means or air injection nozzle in this twist-producing part or component for the injection of an air flow or stream in order to form a rotating air layer in such twist-producing part or component and for sucking the twisted fiber structure or the like into such twist-producing part or component.
An air jet nozzle of this kind is known from German Published Patent Application No. 2,722,319, published Jan. 15, 1981, the European Published Patent Application No. 0,131,170, published Jan. 16, 1985, and German Published Patent Application No. 3,526,514, published Feb. 6, 1986. These documents demonstrate that such air jet nozzles are used as so-called false-twist nozzle in combination with a drafting arrangement. The drafting arrangement delivers a sliver which is subdivided into core fibers and edge fibers. The twist nozzle or, as in the case of the last-mentioned patent document, the second twist nozzle as considered in the direction of yarn movement or travel, rotates the yarn core fibers so as to form a false-twisted yarn core which extends from substantially the twist-producing part or component of this twist nozzle up to the delivery rolls of the drafting arrangement. The air inlet duct or, as in the case of the last-mentioned patent document, the first air jet or twist nozzle as considered in the direction of yarn movement or travel, guides the edge fibers towards the false-twisted yarn core and wraps these edge fibers around the false-twisted yarn core. These fibers which have been wound around the yarn core are designated as wrapping fibers which wrap around the yarn core which is again rotated back or unrotated (and which unrotated yarn has substantially parallel fibers) after departing from the twist-producing part or component of the twist nozzle and thus impart to the yarn the required strength.
It will therefore be readily understood that the fiber feed to the false-twisted yarn core and the subsequent wrapping operation are carried out such that even after the yarn core has been rotated back into its neutral position (in which the fibers lie substantially in the longitudinal direction in the yarn) the wrapping fibers bear sufficiently snugly and with sufficient wraps or convolutions against the yarn core to impart to the yarn the required strength.
It will be apparent from the disclosures of the aforementioned published patent documents that air injection nozzles lead into the twist-producing part of the false-twist air jet nozzle and are directed such that a rotation is imparted to the yarn core arriving from the drafting arrangement. In particular, the yarn core is brought into contact with the inner wall of the twist-producing part by the rotating air flow and the resulting centrifugal force, so that a crank effect or action occurs at the yarn core and imparts to such yarn core the false twist or, where two twist nozzles are used in series or succession, i.e. one after the other in the direction of yarn movement or travel, as disclosed in German Patent No. 3,237,990, published Mar. 13, 1986, the first twist nozzle places the edge fibers against the false-twisted yarn core.
In recognition of the fact that this air flow alone contributes to the aforenoted crank formation or action, and thus, rotation of the yarn core, particular attention has been devoted to such air flow during the course of examining and analyzing such air flow in order to optimize the energy required from the air flow in terms of imparting rotation to the yarn core and to achieve an economical spinning operation. In terms of economic considerations such should be limited to a comparison between energy consumption and spinning speed.
The person skilled in the art concerned with this spinning technique is aware that the air flow must not only impart rotation to the yarn or twisted fiber structure, but also a feed or forwarding effect to the yarn or twisted fiber structure in the direction of yarn movement or travel in order to produce a thread tension component in the false-twisted yarn core.
It is also known from the aforementioned European Published Patent Application No.0,131,170, as shown in FIGS. 4 to 5a, that the air sucked into the inlet duct is sucked away in front of the constriction or throttle location. It is therefore necessary for the air flow to also produce a suction effect in the twist-producing part, apart from the aforenoted yarn rotation and yarn forwarding action, in order to suck air sufficiently through the inlet duct by the air flow flowing into the feed duct, in order to prevent the fiber ends bearing against the false-twisted yarn core from migrating towards the suction produced in the inlet duct.